1. Field of the Invention
The present invention relates to a color liquid crystal display (LCD) which employs a voltage control birefringence method for controlling the tilt direction of, for example, vertically-alignment liquid crystal by using an electric field.
2. Description of the Prior Art
LCDs, in which liquid crystal is enclosed between a pair of substrates and a voltage is applied to the enclosed liquid crystal for desired display are advantageously small and thin, and the power consumption thereof can be easily reduced. Due to these advantages, LCDs are widely used as displays in various office automation equipment, such as personal computers, and audio visual equipment, such as a projector, and portable or on-board devices.
In particular, a DAP (deformation of vertically aligned phase) LCD is proposed, which includes liquid crystal with negative dielectric constant anisotropy, and controls initial alignment of the liquid crystal molecules so as to be vertically-aligned by using a vertical alignment layer. Specifically, a DAP LCD employs one type of electrically controlled birefringence (ECB) methods, and controls transmittance and displayed colors of the light coming into the liquid crystal layer by utilizing a difference in a reflective index between the longer and shorter axes of a liquid crystal molecules, i.e., a birefringence phenomenon. A pair of substrates are provided each with a polarization film attached on the outer surface thereof, such that their polarization directions are orthogonal to each other. When voltage is applied to the liquid crystal layer, linearly polarized light which has been introduced into the liquid crystal layer via the polarization film on one side of the substrate is converted into elliptically or circularly polarized light due to birefringence thereof of the liquid crystal layer, and is partly ejected from the polarization film on the other side. Since the extent of birefringence of the liquid crystal layer, i.e., a phase difference (a retardation amount) between ordinary and extraordinary ray components of the incoming linearly polarized light, is determined according to the voltage applied to the liquid crystal layer, i.e., the intensity of an electric field generated in the liquid crystal, the amount of light ejected from the second polarization film can be controlled for every pixel by controlling for every pixel the voltage applied to the liquid. crystal layer. This eventually makes it possible to display a desired color image when RGB color filters and RGB light sources are used.